Pressurized ducts of medium and large size, for example for transporting pressurized fluids such as fuels (liquid or gaseous) or the like, are generally provided with one or more branches through which it is possible to access the inside of the duct. These branches define accesses that allow apparatus to be inserted into the duct to perform inspections, cleaning and/or maintenance operations.
Generally, these branches comprise a section of pipe, which connects on the lateral surface of the main duct, fitted on the free end of which is a closure that allows sealing of said section of pipe when the duct is filled with the pressurized fluid.
Known closures generally comprise an annular element, fitted to the free end of the pipe, which define an opening through which the duct can be accessed. Said opening can be closed hermetically by means of a movable hatch connected in an articulated manner to said annular element.
The seal of the closure is generally guaranteed by two abutment surfaces, obtained respectively on the hatch and on the annular element, between which a gasket is interposed.
This gasket, made of a resilient material such as rubber or the like, is generally housed in a seat obtained on the hatch or, at times, on the annular element.
Examples of closures for pressurized ducts thus structured are described in EP 1843065 B1, WO 02/097319 A1 and U.S. Pat. No. 7,341,161 B2.
However, these known closures can only be fitted to ducts in which the pressure of the fluid does not exceed values of around 500 bar.
In fact, above this threshold the pressurized fluid, which normally penetrates the gap between the two abutment surfaces, presses on the gasket, to such an extent as to deform it and thrust it toward the outside of the closure.
In these conditions, the gasket is therefore unable to contain the fluid, which can escape from the closure.
The higher the pressure of the fluid is, the more evident this phenomenon is.
In this context, the object of the present invention is to provide a closure for pressurized ducts or receptacles that solves the problems of the prior art described above.
It is therefore an object of the present invention to provide a closure that can guarantee seal even at pressures of the fluid greater than 1000 bar, for example up to 2000 bar.
Another object of the present invention is to provide a closure that is reliable and with parts that are not subject to wear and, therefore, which do not require frequent periodic maintenance.
A further object of the present invention is to provide a closure that is practical and easy to handle.
In addition to the above, an object of the present invention is also to provide a closure that is simple and inexpensive to produce.
These objects are achieved by a closure for ducts or receptacles for pressurized fluids, which comprises:                a supporting structure, to be fitted to a free end of a section of a tubular element, which defines an opening for accessing the duct or receptacle, and,        a hatch, connected in an articulated manner to said supporting structure, with the ability to move between a closed position and an open position.        
The closure according to the invention can be fitted to ducts or receptacles intended to transport or contain pressurized fluids, such as fuels (liquid or gaseous), water or the like.
More in general, the closure of the invention can therefore be fitted to hollow bodies intended to contain a pressurized fluid, either static or moving.
Therefore, in the description below, the term “duct” or “pressurized duct” relates to a generic hollow body among those mentioned above.
At the opening thereof, the supporting structure is provided with an annular sealing surface that extends from the opening toward the tubular element, along a direction X.
The closure according to the invention comprises a sealing element that, when the closure is closed, is arranged in the opening.
Said sealing element comprises an expansible portion with an inner surface, which faces the duct, and an outer surface, facing the sealing surface of the supporting structure.